66,833 research outputs found
The ALPINE-ALMA [C II] survey: Star-formation-driven outflows and circumgalactic enrichment in the early Universe
We study the efficiency of galactic feedback in the early Universe by stacking the [C II] 158 μm emission in a large sample of normal star-forming galaxies at 4 4. From the stacking analysis of the datacubes, we find that the combined [C II] core emission (|v|< 200 km s⁻¹) of the higher-SFR galaxies is extended on physical sizes of ∼30 kpc (diameter scale), well beyond the analogous [C II] core emission of lower-SFR galaxies and the stacked far-infrared continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochs
Detections of water ice, hydrocarbons, and 3.3um PAH in z~2 ULIRGs
We present the first detections of the 3um water ice and 3.4um amorphous
hydrocarbon (HAC) absorption features in z~2 ULIRGs. These are based on deep
rest-frame 2-8um Spitzer IRS spectra of 11 sources selected for their
appreciable silicate absorption. The HAC-to-silicate ratio for our z~2 sources
is typically higher by a factor of 2-5 than that observed in the Milky Way.
This HAC `excess' suggests compact nuclei with steep temperature gradients as
opposed to predominantly host obscuration. Beside the above molecular
absorption features, we detect the 3.3um PAH emission feature in one of our
sources with three more individual spectra showing evidence for it. Stacking
analysis suggests that water ice, hydrocarbons, and PAH are likely present in
the bulk of this sample even when not individually detected. The most
unexpected result of our study is the lack of clear detections of the 4.67um CO
gas absorption feature. Only three of the sources show tentative signs of this
feature and at significantly lower levels than has been observed in local
ULIRGs. Overall, we find that the closest local analogs to our sources, in
terms of 3-4um color, HAC-to-silicate and ice-to-silicate ratios, as well as
low PAH equivalent widths are sources dominated by deeply obscured nuclei. Such
sources form only a small fraction of ULIRGs locally and are commonly believed
to be dominated by buried AGN. Our sample suggests that, in absolute number,
such buried AGN are at least an order of magnitude more common at z~2 than
today. The presence of PAH suggests that significant levels of star-formation
are present even if the obscured AGN typically dominate the power budget.Comment: 39 pages, 14 figures, accepted for publication in Ap
Would Global Patent Protection be too Weak without International Coordination?
This paper analyzes the setting of national patent policies in the global economy. In the standard model with free trade and social-welfare-maximizing governments à la Grossman and Lai (2004), cross-border positive policy externalities induce individual countries to select patent strengths that are weaker than is optimal from a global perspective. The paper introduces three new features to the analysis: trade barriers, firm heterogeneity in terms of productivity and political economy considerations in setting patent policies. The first two features (trade barriers interacting with firm heterogeneity) tend to reduce the size of cross-border externalities in patent protection and therefore make national IPR policies closer to the global optimum. With firm lobbying creating profit-bias of the government, it is even possible that the equilibrium strength of global patent protection is greater than the globally efficient level. Thus, the question of under-protection or not is an empirical one. Based on calibration exercises, we find that there would be global under-protection of patent rights when there is no international policy coordination. Furthermore, requiring all countries to harmonize their patent standards with the equilibrium standard of the most innovative country (the US) does not lead to global over-protection of patent rights.intellectual property rights, patents, TRIPS, harmonization
On measuring the Tully-Fisher relation at
The evolution of the line width - luminosity relation for spiral galaxies,
the Tully-Fisher relation, strongly constrains galaxy formation and evolution
models. At this moment, the kinematics of z>1 spiral galaxies can only be
measured using rest frame optical emission lines associated with star
formation, such as Halpha and [OIII]5007/4959 and [OII]3727. This method has
intrinsic difficulties and uncertainties. Moreover, observations of these lines
are challenging for present day telescopes and techniques. Here, we present an
overview of the intrinsic and observational challenges and some ways way to
circumvent them. We illustrate our results with the HST/NICMOS grism sample
data of z ~ 1.5 starburst galaxies. The number of galaxies we can use in the
final Tully-Fisher analysis is only three. We find a ~2 mag offset from the
local rest frame B and R band Tully-Fisher relation for this sample. This
offset is partially explained by sample selection effects and sample specifics.
Uncertainties in inclination and extinction and the effects of star formation
on the luminosity can be accounted for. The largest remaining uncertainty is
the line width / rotation curve velocity measurement. We show that high
resolution, excellent seeing integral field spectroscopy will improve the
situation. However, we note that no flat rotation curves have been observed for
galaxies with z>1. This could be due to the described instrumental and
observational limitations, but it might also mean that galaxies at z>1 have not
reached the organised motions of the present day.Comment: 13 pages, 7 figures, A&A accepte
K-essence Explains a Lorentz Violation Experiment
Recently, a state of the art experiment shows evidence for Lorentz violation
in the gravitational sector. To explain this experiment, we investigate a
spontaneous Lorentz violation scenario with a generalized scalar field. We find
that when the scalar field is nonminimally coupled to gravity, the Lorentz
violation induces a deformation in the Newtonian potential along the direction
of Lorentz violation.Comment: 8 pages, the final version, discussion and references adde
Bias-induced insulator-metal transition in organic electronics
We investigate the bias-induced insulator-metal transition in organic
electronics devices, on the basis of the Su-Schrieffer-Heeger model combined
with the non-equilibrium Green's function formalism. The insulator-metal
transition is explained with the energy levels crossover that eliminates the
Peierls phase and delocalizes the electron states near the threshold voltage.
This may account for the experimental observations on the devices that exhibit
intrinsic bistable conductance switching with large on-off ratio.Comment: 6 pages, 3 figures. To appear in Applied Physics Letter
|V_ub| and |V_cb|, Charm Counting and Lifetime Differences in Inclusive Bottom Hadron Decays
Inclusive bottom hadron decays are analyzed based on the heavy quark
effective field theory (HQEFT). Special attentions in this paper are paid to
the b\to u transitions and nonspectator effects. As a consequence, the CKM
quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the
inclusive semileptonic decays B\to X_u e \nu and B\to X_c e \nu. Various
observables, such as the semileptonic branch ratio B_SL, the lifetime
differences among B^-, B^0, B_s and \Lambda_b hadrons, the charm counting n_c,
are predicted and found to be consistent with the present experimental data.Comment: 20 pages, Revtex, 4 figures and 2 table
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